As I mentioned earlier in this thread, there is another person I've been talking to on AV123, and he is having the same issue with his Denon 2807, MPS-1, and 4ohm Ref 1's.

I think the amp was just engaging its protective circuitry as I approached its limits. Based on my figures, 119 dB would require 256 watts. The MPS-1 is rated at 300 watts into 4 ohms. I was taking my measurements from 13 feet away, as I moved closer to my m80's, I was easily reaching 120dB and beyond during peaks.

ps: I did have my hearing buds in to protect my ears.

Below is some more information I found on Audioholics review by Gene. I will be following up with Emotiva.

" Later on the bench I discovered that the MPS-1 was engaging its soft clipping circuit at around 37-38Vrms into 8 ohm loads and while driving 4 ohm loads the MPS-1 delivered about 31Vrms into 4 ohm load unclipped (note the RBH T-2 System has 4 ohms impedance). However, as I increased the signal level just below clipping, I was able to achieve 33Vrms at 1kHz but the amp shut off when frequency was brought down below 60Hz. It was apparent the sensitivity of the soft clipping circuit / limiter needed some tweaking. I informed Emotiva of my findings and they quickly resolved this issue, sent me a new sample and I didn't observe this problem thereafter"

And This: "I was able to achieve a maximum unclipped power of 175wpc into 8 ohms with Vin=1.65V Vout=37.39V unbalanced and about 255wpc into a 4 ohm load with Vin = 1.42V and Vout = 32V. Once I exceeded these measurements, the clamping circuit kicked in rounding off the signal and dramatically increasing distortion. Based on this, I would rate this amp to be a 175wpc into 8 ohms and 270wpc into 4 ohm, not 200wpc / 300wpc 8/4 ohm respectively like Emotiva rated in their literature."

Randy, the only thing that I'd think would be even mildly disturbing in the additional quotes from Gene's test is the protective circuit shutting it down as he described, but this supposedly was corrected and you'd think that this also applied to later production units.

As far as the numbers in the second paragraph, they all figure and are good. 1.42v in and 32v out is a gain of 27dB[20 log(32/1.42)], as Gene mentioned elsewhere, and the resulting power from Ohm's Law(P=Vsquared/R)is 1024/4= 256 watts.

By the way, my calculations for 106dB at your listening position came up about 100-110 watts into 4 ohms.

Thanks John, I"ve been on the phone with Emotiva today. They assured me my problem was not the Soft Clipping issue that Audioholics talked about. Also, every new unit after that point was fixed based on the Audioholics review.

We are looking at a few things, and they are willing to send me out some new modules if I say the word. This is unlikely, but they said it is possible that the Bias adjustment may be a little off on my units, and causing the amp to shut down prematurely. They are still leaning towards that I may be bouncing of the upper limit of the amplifier.

I just don't think that is the issue, but maybe. They also recommended that I DO NOT use my Tripplite surge/conditioner, and just plug the amp right into the wall outlet directly. They also said they recommend, if possible, that a person uses a dedicated line just for the amp. The Tripplite can be limiting what the amp is receiving, especially during dynamic times when the amp needs more current. Also, the amp, being a class H design, has built in protection, so they do not recommend a surge/conditioner.

In regards to Audioholics findings of 256 watts into 4 ohms, they assured me that they are in fact 300watts into 4 ohms as stated. They are not sure of the exact test that was used to get these figures (mainly what equipment/ load banks, etc.), but they assured me and will back their specs up every day of the week that their amps do produce the power that they are rated. This is something Emotiva takes very seriously and they do not play games with the figures.

In regards to me worrying about the Denon's 1.2v preout rating, here is their response:

The EPM-300 amplifier modules are set to 27db of gain with a 0db reference input level of 1.5 volts nominal. That is to say that the amps have 27db of gain and that it would take a steady state tone at 1.5 volts to get maximum output. Now the amps can easily take a voltage input well in excess of this with no problems to recreate the dynamics of the source material. However, if you pre/pro is rated at 1.2 volts, then yes it is possible to get a clipped signal out of the pre/pro, but unlikely. The 1.2 volt rating is a nominal rating that means under a steady state test that is what it will produce before clipping. However, music is not a steady state; it is all about the dynamics, so the actual output could be well in excess of 2.0 volts.

Ok, after plugging the amp directly into the outlet, as I mention above, I was hoping the problem was resolved.

From the seated position, 13ft away, my m80's are at +5dB to achieve 75dB on the SPL meter, using the Denon's test tones.

Should I be using the test tones on the receiver, I would think 75dB is 75dB, no matter what the source of the calibration setup?

Anyway, I turned on some music with the Denon main volume on -5dB (pretty loud) and things sounded great. So I eased it up to 0dB on the volume, still sounded great. The meter set to "fast" with C-weighting was basically averaging 100dBs. Even when I walked up to about 3 ft of either m80, was not even hitting 110dB's, at least what I could see visually with the SPL meter.

So, I went back to my easy chair from 13ft away and eased the knob up to +5dB. After about 10 seconds, the left channel amp turned off, followed by the right channel shortly after.

I guess the Tripplite had nothing to do with anything. I will be calling Emotiva back to see what they think. I wish I had another Receiver to rule out my Denon preouts. There is another guy on Av123 having the same problem with his Denon 2807 running Ref 1's (4ohm).

Is it just the combination of my 80's and Denon. Emotiva is going out of their way to help me, and they assure me this Class H amp, their top of the line, is designed to be pushed hard. This is so frustrating.

I'm wondering if I should be calibrating my speakers, NOT using the Denon?

I agree with your consensus, a calibration to 75db is a calibration to 75db. Your SPL meter doesn't lie. Regardless of calibration, you are still not pushing the amp as much as other say it can be pushed.

I don't know much about denon's at all, can't help you there.

Perhaps you have a fellow audiophile friend locally that could do a listening test with his reciever or something.

Ok, I did some testing just now, thanks to Wid for giving me the idea. I hooked up my rear Qs8's to my amp. They are rated at 400 watts also, so what the heck. Now I know they are 6 ohm, versus the 4ohm 80's. But this might help to tell us what is going on if anything.

Also, just for safety, I turned my crossover to 100hz, since the Q's were now hooked to the left/right channels and would be really tested.

I used the song "Take it on the Run" by REO. With the Qs8's, I gradually turned up the volume from 0, to +3, to +6, to +10. Even though they are rated at 400watts, I was a little worried, so I didn't go beyond +10, however, I did leave it at +10 for a couple of minutes. Everything was fine and neither monoblock turned off.

So then I rehooked up my 80's and started the same song over. At 0, everything was fine and the sound was killer. then I turned it to +3 for a minute still ok, then +4 BAMMMMMMM as soon as the kick drum and bass guitar kicked in during a dramatic part of the song when they say "Take it on the run baby", the left main shut down. If I would have let it go, eventually the right amp would have shut down also, but I just turned everything off and was pissed.